Interest in using saliva as a diagnostic tool for disease detection and health surveillance is increasing due to its noninvasive accessibility, cost-effectiveness, easy sample collection and processing, and accumulating scientific rationale (Yan et al., Proteomics Clin. Appl. 3:116 (2009); Lee and Wong, Am J. Dent. 22:241-8 (2009)). Saliva has been used to detect, for example, caries risk, peridontitis, oral cancer, breast cancer, lung cancer, Sjögren's syndrome, salivary gland disease and infectious diseases such as hepatitis, HIV, and HCV. Saliva is therefore an attractive diagnostic sample alternative for blood, serum, or plasma.
Saliva is ideal for nucleic acid analysis. The human salivary transcriptome in cell-free saliva was first discovered in 2004 by use of microarray technology (Li et al, J. Dent. Res. 83:199-203 (2004)). Investigations into the characteristics of salivary RNA followed, which led to the development of salivary transcriptomics as a research focus. (Park et al., Clin. Chem 52:988-94 (2006); Park et al. Arch. Oral. Biol., 52:30-5 (2007)).
Saliva is additionally ideal for proteomic analysis. Profiling proteins in saliva over the course of disease progression can reveal biomarkers indicative of different stages of diseases, which can be useful in early detection and/or medical diagnosis (Hu et al., Proteomics 6:6326 (2006)). Proteomics is widely envisioned as a unique and powerful approach to biomarker development. As proteomic technologies continue to mature, proteomics has the great potential for salivary proteomic biomarker development and further clinical applications (Xiao and Wong, Bioinformation 5:294 (2011); Zhang et al, Mol. Diagn. Ther. 13:245 (2009)).
However, current methods for the extraction of nucleic acids and protein from saliva require the saliva sample to be processed immediately after collection requiring special instrumentation and trained personnel. For example, current standard procedures for salivary transcriptomic diagnostics require mRNA isolation, which is time-consuming and labor-intensive. In addition, operator differences increase as procedural complexity increases. Although several automated devices are commercially available to enhance mRNA isolation efficiency (e.g., KING FISHER<QIACUBE, and MAXWELL 16), throughput is still limited by the number of samples processed per run. Furthermore, particular care is required when working with RNA because of its inherent instability and the ubiquitous presence of RNases. Likewise, current standard procedures for salivary proteomic diagnostics require the addition of protease inhibitors to prevent proteolysis. As a result, current methods for transcriptomic and proteomic diagnostics require the addition of nucleic acid and protein stabilizers to be added to saliva samples followed by storage at −80° C.
The ability to analyze saliva to monitor health and disease is a highly desirable goal for oral health promotion and research. In order to fully realize the diagnostic and research uses of saliva as a source of biomarkers, systems for collection, handling, and room-temperature storage of saliva by non-professionals in a user friendly integrated point-of-care collection system are desirable.